Machine for sharpening lawn mowers



March 30, 1943. J. P. MAYNARD ETAL v 2,314,$45 v MACHINE FOR SHARPENING LAWN-MOWERS Filed June 1, 1940 5 'Sheets-Shet 1 March 30, 1943. I Q J. P..MAYNARD ETAL $314,945

MACHINE FOR SHARPENING LAWN-MOWERS Filed June 1, 1940 3 Sheets-Sheet 2 AL MUM I wn rigs:

: W JWW Patented Mar. 30, 1943 MACHINE FOR SHARPENING LAWN MOWER-S Joel P. Maynard, Pawtucket, and George A. Matteson, Jr., Saunderstown, It. I., assignors to The Graham Mfg. 00., Inc., a corporation of Rhode Island Application June 1, 1940, Serial No. 338,348

1 Claim.

This invention relates to lawn-mower grinding machines and more particularly to improvements in machines of the type illustrated and described in United States Letters Patent to Purdom Carpenter, No. 2,142,669, issued January 3, 1939.

.One of the objects of the present invention is to provide a machine of the type indicated wherein a lawn-mower reel is rotated and the reel and grinding tool relatively traversed to produce cylindrical surface grinding.

Another object of the invention is to provide a machine of the type indicated having an improved reversing mechanism for automatically reversing the direction of relative traverse of the reel and grinding tool.

Another object of the invention is to provide a machine of the type indicated having an improved driving means for rotating the lawnmower reel.

Another object of the invention is to provide a traverse-reversing mechanism and driving means for rotating the lawn-mower reel adapted to be mounted on machines of usual construction as an attachment and driven by a common driving element.

Still another object of the invention is to provide an attachment for a machine of the type indicated which is of relatively simple construction while at the same time efficient in performing its intended functions.

Further objects of the invention are set forth in the following specification which describes a preferred form of construction of the machine, by way of example, as illustrated by the accompanying drawings. In the drawings:

Fig. 1 is a front elevational view of a lawnmower grinding machine showing the reversing mechanism for operating the traversing means and the means for rotating the lawn-mower reel;

Fig. 2 is an end elevational view showing the single motor for driving the reversing mechanism for the traversing means and the means for rotating the lawn-mower reel;

Fig. 3 is a plan view partly in Section on line 3-3 of Fig. 1;

Fig. 4 is a front elevational View of the reversing mechanism shown in neutral position to adapt the traversing mechanism to be operated manually;

Fig. 5 is a View similar to Fig. 4 showing the reversing mechanism in a position of adjustment opposite from that illustrated in Fig. 1;

Fig. 6 is an enlarged view of the clutch for coupling the lawn-mower reel to its driving means;

Fig. 7 is a View similar to Fig. 6 showing the clutch as turned from the position illustrated in Fig. 6;

Fig. 8 is a transverse sectional view taken on line 8 -B of Fig. 6 and showing the interlocking arms on the driving head and dog of the clutch to provide a flexible driving connection;

Fig. 9 is a plan view showing the push rod for operating the reversing mechanism in one of its extreme, positions; and

Fig. 10 is a view similar to Fig. 9 showing the push rod as moved to its opposite extreme position to operate the reversing mechanism.

The present invention relates, in general, to a lawn-mower grindingmachine having automatically operated mechanism for reversing the direction of relative traverse of the grinding tool and lawn-mower reel to be ground and means for continuously rotating the reel to produce cylindrical surface grinding. The reversing mechanism comprises a worm-wheel mounted on a driven shaft for operating the traversing mechanism and a movable frame in which a pair of continuously rotating worm-gears or the like are journaled. The worm-gears are positioned ad jacent the periphery of a worm-wheel at opposite sides thereof and a cam actuated by the relatively traversing tool and reel operates the movable frame to simultaneously engage one of the worm-gears with the worm-wheel and disengage the other Worm-geartherefromto reverse the direction of traverse. The means for driving the lawn-mower reel is adjustable on the machine frame to adapt it for connection to reels of dif'! ferent size and the arrangement of the parts is such that the reversing mechanism and driving means for rotating the lawn-mower reel are driven from a common driving element.

Referring to the drawings, the machine incorporating the novel features of the present invention is generally similar to that-shown and described in the United States Letters Patent to Purdom Carpenter referred to above. Suflice, it

to state herein that the machine comprises a frame having end-standards .l and 2 held in spaced relationship by tie-rods 3, 4, 5 and 6 con-. nected at their ends tothe standards. Extending transversely of the machine in spaced, apart relationship are supporting rods 9 which are pivotally connected tofthetie-rod 4 at their rearward ends and to jack-screws Ill-at their forward ends. The jack-scre'ws Ill are so constructed and arranged as to adapt the forward ends of therods 9 to be raised or lowered When. the. screws are turned. Mounted on the rods 9 are, blocks ll adapted to be moved forwardly and rearwardly longitudinally thereof by means of adjusting screws l2. The blocks support a shaft |3 extending transversely of the rods 9 and mounted to rock on the shaft is a supporting cradle as described hereinafter.

The cradle comprises elbow-shaped members I6 pivotally mounted in spaced relationship on the shaft l3 and a transverse angle-iron rail or bed connecting the ends of the arms l3 of the members IS. The arms H! of the members l6 are adapted to detachably mount the stationary blade of a lawn-mower while, the opposite arms l9 are adapted to support the reel R of a lawn-mower to be ground. The arms l9 have notches 26 at their upper ends for receiving the tie-rod 2| of the lawn-mower fram withclamps 22 for clamping the tie-rod in the notches, see Figs. 1 and 2. An adjustable bracket 23 extending upwardly from the machine frame tie-rod 3 is adapted to support the roller 24 of the lawnmower to locate the blades 1 of the reel R in position to be ground. The cradle is rockable from one to the other of two positions and as illustrated in Fig. 2 the arms l8 and I9 have notches 25 for receiving the shanks of bolts 26, see Fig. 1, projecting laterally from the blocks I on the rods 9, wing-nuts 21 being screwed onto the bolts 26 and tightened against the arms |6 and I3 to clamp the cradle in one or the other of its two positions on the frame. It will be understood that other structures may be provided for supporting the stationary blade and reel R, either mounted in or detached from the mower, in position to be traversed by the grinding-wheel.

The grinding means comprises an abrasive wheel 30 adapted to traverse the stationary blade or blades 1' of the reel R to be ground. The grinding-wheel 36 is mounted for rotation on a shaft 3| at one side of a carriage 32 and is driven from an electric motor 33 on the carriage by a belt 34 connecting suitable pulleys 28 and 29. The carriage 32 has depending bearings 35 which embrace the tie-rod to mount the carriage to rock and slide thereon. Thus, the tie-rod 5 constitutes a track for guiding and supporting the carriage 32. The grinding-wheel 36 and motor 33 are preferably arranged on the carriage 32 on opposite sides of the track 5 to substantially counterbalance each other with a slight overbalance on the wheel side. The rocking movement of the carriage 32 on its supporting track 5 is controlled by an adjustable linkage connecting the carriage to the frame tie-rod 6, which latter also constitutes a guiding track therefor. The linkage comprises a guard 36 for the wheel 30 attached to the shaft 3| and an adjustable rod 31 connecting the guard to a bearing 38 slidable on the guiding track 6. As illustrated in Fig. 2 the upper end of the rod 31 is clamped in the bearing 38 by means of thumb-screws 39 to permit its vertical adjustment and the lower end of the rod has screw-threads 46 which cooperate with the threaded bore of a nut 4| closely fitting between the sides of a slot 42 in a bearing 43 surmounting the guard 36. Thus, the linkage provides a rigid connection between the carriage 32 and the bearing 38 on the guiding track 6. The bearing 38 has spaced hubs embracing the guiding track 6 and is adapted to slide thereon as the carriage is moved along its supporting track 5.

4 The carriage 32 is traversed longitudinally of the machine by means of flexible driving means, see Fig. 1, comprising a cable section 44 having one end attached to the carriage at 45 and a chain section 46 having one end connected to the cable section and its opposite end attached to the carriage at 41. The cable section 44 passes around a pulley 48 suitably mounted on the standard of the frame, while the chain section passes around a sprocket 49 of a driving and reversing mechanism for the traversing means as next explained.

In accordance with the present invention, a novel form of driving and reversing mechanism for the traversing means is provided comprising a driven wheel 53 and a pair of driving elements 54 and 55 at opposite sides of the driven wheel and alternately engageable therewith. The driven wheel 53 is illustrated in the form of a worm-wheel mounted on the forwardly projecting end of a shaft 56 journaled in suitable spaced bearings 51 in a bracket 58, see Figs. 1 and 3. The bracket 58 is attached to the outside of the standard 2 of the machine frame by means of bolts 59 to adapt the driving and reversing mechanism of the present invention to be mounted on standard machines as an attachment therefor. The shaft 56 mounts the sprocket 49, previously referred to, between the bearings 51. A crankhandle 66 may be mounted on the forward end of the shaft 56 for turning the latter manually and between the hub of the crank-handle and the forward bearing 51 of the bracket 58 is a sleeve 6| having a reduced rearwardly extending end portion 62 with a slot 63 therein as shown in Fig. 3. The sleeve 6| is normally held in its forward position illustrated in Figs. 2 and 3 by the engagement of its reduced end portion 62 with a pin 64 projecting radially from the shaft 56. The sleeve 6| is slid rearwardly on the shaft 56 when the slot 63 therein is alined with the pin 64 by means of a coil-spring 65 acting between the rearward end of the hub of the crank-handle 66 and the forward end of the sleeve 6|.

The driving elements 54 and 55, herein illustrated as shafts with screw-threads or helical worm-teeth formed thereon, are journaled in a movable frame or casing 61 embracing the wormwheel 53 and are positioned at oppositesides of the latter. As illustrated most clearly in Fig. 1, the worm-gears 54 and 55 are held against axial movement in the casing 6! by collars 68 fastened to their reduced end portions with their opposite end portions projecting from the casing and carrying pulleys 69 and 10 fixed thereto. The casing 61 has a removable front cover-plate 12 provided with a centrally located circular hole 13 therein through which the shaft 56 extends, see Fig. 3. The hole 13 in the cover-plate 12 is of sufiicient diameter to adapt the casing 61 to rock from one to the other of its two positions illustrated in Figs. 1 and 5 and is of substantially the same diameter as the reduced end portion 62 projecting from the sleeve 6|. When the reduced end portion 62 of the sleeve 6| is projected rearwardly into the hole 73 in the cover-plate 12 of the casing 61 it maintains the latter in its neutral position illustrated in Fig. 4, at which time the worm-gears 54 and 55 are both disengaged from the worm-wheel 53, The threads on the worm-gears 54 and 55 advance in the same direction and the worm-gears are continuously rotated by a belt 14 extending around the pulleys 66 and 16 on the worm-gears and a pulley 15 on the drive shaft of an electric motor 16, see Fig. 2. The motor 16 is mounted on a platform I! projecting rearwardly from the bracket 58 and for purposes of adjustment the platform is pivotally connected to the bracket and rendered adjustable by means of a set-screw I8.

Although the casing 6! may be adapted for movement in any suitable manner, as herein illustrated it is mounted on the forward end of a rock-shaft II journaled in suitable bearings in the bracket 58 and spaced laterally from the shaft 58. Depending from the rearwardly projecting end of the rock-shaft 'II is an actuating arm 88 having a follower or roller 8| at its end. The casing 61 is rocked from one to the other of its two positions illustrated in Figs. 1 and 5 by means of an over-center cam 82 cooperating with the roller BI on the actuating arm 88. As herein illustrated the over-center cam is in the form of a hollow arm 88 pivotally mounted at its lower end between spaced arms 84 depending from the bracket 58. A plunger 85 in the hollow arm 83 is normally urged outwardly with respect thereto by a spring 88 and the upper end of the plunger has oppositely inclined cam faces 87 and 88 engageable with the roller 8! on the actuating arm 88. Thus, when the over-center cam 82 is rocked from the position illustrated in Fig. l to that illustrated in Fig. 5 the engagement of the inclined cam-face 81 with the roller 8! causes the plunger 85 to slide into the hollow arm 83 as the peak of the cam passes across the axis of the roller. After the peak of the cam 82 has passed across the axis of the roller M the opposite inclined face 88 acting on the roller will rock the actuating arm 88 and rock-shaft II connected thereto which, in turn, rocks the casing 81 to disengage the worm-gear 55 from the wormwheel 53 and engage the worm-gear 58 therewith. The extent of rocking movement of the over-center cam 82 is limited by the engagement of its hollow arm 83 with adjustable stops 95 and 98 on the bracket 58, see Fig. 5, to maintain one or the other of the cam-faces 81 or 88 in engagement with the follower or roller 8|.

To provide for automatic operation of the reversing mechanism a lever 89 attached to the side of the hollow arm 83 projects upwardly through a looped strap 98 on a push rod 9|. The push rod 9i is mounted for sliding movement through the web of the bracket 58 attached to the standard 2 and a bracket 94 attached to the standard I, see Fig. 1, and has adjustable stops 92 and 93 fixed thereon in position to be engaged by the carriage 32 during its traverse on the track 5 of the machine frame. Thus, as the carriage 32 moves to the left as viewed in Fig. 1 it engages the stop 92 on the push rod 9| to slide the latter to the left as viewed in Fig. 10 causing the looped strap 88 at its right-hand end to actuate the lever 89 to rock the over-center cam 82 to the position illustrated in Fig. 5.

In accordance with the present invention driving mechanism is provided for rotating the lawnmover reel R during the relative transverse of the reel and grinding tool 38 whereby to produce a cylindrically ground surface. To this end a countrshaft 88 is journaled in bearings at the bottom of the standards I and 2 of the machine frame and has one end projecting beyond the standard 2 with a pulley 99 fast thereon in alinement with a pulley I88 on the drive shaft of the motor I8, the two pulleys being drivingly conneoted by a belt 91. On the countershaft 98 between the standards I and 2 is a roller which in effect constitutes an elongate pulley IN. A drive shaft I82 adapted for alinement with the shaft of the lawn-mower reel 1% is journaled in a bearing I83 on an arm I84 adjustably mounted on a cross-strut I extending between the tie-rods 3 and 4 of the machine frame. The shaft I82 mounts a pulley I88 at one side of the gearing I83 and has a yoke-shaped driving head I8'I at the opposite side of the bearing comprising one of the elements of a flexible coupling I88, shown in detail in Figs. 6 to 8. The shaft I82 is slidable in the bearing I83 and is normally held in the position illustrated in Fig. l by means of a spring I89 acting between the bearing and the drivinghead I81.

The spaced arms H8 and III of the yokeshaped driving head I8! are adapted for driving engagement with the radially extending arms I I2 and H8 of a dog II4 detachably clamped to the shaft 8 of the lawn-mower reel R and comprising the other element of the flexible coupling I88, see Figs. 6 and '7. The dog H4 consists of com.- plementary jaws H5 and H8 having angular grooves II! to adapt them at one end to fit the shafts of lawn-mower reels R of different dimensions. A plug II8 havinga series of stepped shoulders is adapted for insertion into the opposite end of the dog II I between the jaws H5 and H8 to provide a filler element of substantially.

the same diameter as the shaft 8 of the lawnmower reel R. The plug H8 is held in place by an eye-bolt II9 extending axially of the dog II4 between the jaws H5 and H8 and the latter are clamped to the shaft of the lawn-mower reel R by a bolt I28 extending diametrically through the jaws and through the eye of the bolt II9 of the plug II8.

The arm I84 mounting the shaft I82 is provided with a longitudinally extending slot I25 for adjust-ably connecting it to the cross-strut I85 by means of a clamp I28 embracing the crossstrut and having a bolt I21 and threaded stud I28 projecting through the slot in the arm. The clamp I26 is slidable on the cross-strut I85 to adjust the shaft I82 laterally of the machine and the arm I84 is slidable vertically with respect to the clamp I28 to adjust the height of the shaft, the arm being clamped in adjusted position by means of a finger nut I29 screwed onto the threaded stud I28 and tightened against the arm. The cross-strut I85 is also slidable laterally.,along the tie-rods 3 and I on which it is mounted to adjust the shaft I82 longitudinally of the machine, the cross-strut being held in adjusted position by clamps I38 and I3! embracing the tierods. Thus, the relative position of the shaft I82 may be adjusted to approximate alinement with the shaft s of the lawn-mower reel R and the flexible coupling I88 will compensate for any slight misalinement.

The shaft I82 is driven by a belt I32 extending around the pulley I85 thereon, the pulley I8I on the countershaft 98 and an idler pulley I33 mounted on an arm I38 adjustably mounted on the cross-strut I85. to the cross-strut I85 by means of a clamp I35 and nut I38 similar to the clamp I25 and nut I29 described previously. A preferred embodiment of the invention having now been described in detail the method of operation of the machine is explained as follows:

The dog II4 of the flexible clutch I89 is first clamped to the end of the shaft s of the lawnmower reel R. to be ground. To this end the clamping bolt I28 is loosened to adapt the jaws H5 and N8 of the dog II4 to receive the end of the shaft 8 and the stepped shoulder on the plug II 8 most nearly approaching the diameter of said shaft is inserted between the jaws of the-dog The arm I34 is connected.

at its opposite end. The clamping bolt I20 is then tightened to clamp the dog I I4 to the shaft. The reel is then mounted in the machine on the arms I9 of the cradle and bracket 23. The arm I04 is adjusted vertically and horizontally on the cross-strut I35 to aline the shaft I02 with the shaft s of the reel R and the cross-strut is adjusted along the tie-rods 3 and 4 to bring the arms I I and I I I of the yoke-shaped driving head In! into position to engage the radially projecting arms H2 and H3 of the dog H4. The arm I34 is then adjusted on the cross-strut I05 to position the idler pulley I33 to tighten the driving belt I32. The abrasive wheel I3!) is also roughly adjusted by loosening the thumb-screws 39 and moving the adjustable rod 31 with respect to the bearing 38 and the position of the wheel is then accurately adjusted by turning the nut II on the screw-threaded portion 40 of the rod. The machine is now ready for a grinding operation.

With the reversing mechanism in its position of adjustment illustrated in Fig. 1 the driving motor I5 operating through the belt I4 and pulleys 59 and Ill will rotate the worm-gear 55 and worm-wheel 53 in mesh therewith to rotate the shaft 56 in counterclockwise direction. The sprocket 49 on the shaft 56, meshing with the links of the chain section 46 of the flexible driving means will thus cause the carriage 32 carrying the abrasive wheel 3!] to be traversed toward the left as viewed in Fig. l. Simultaneously, with the traversing movement of the carriage 32 the lawn-mower reel R is rotated by the drive comprising the flexible coupling I08, shaft I02, belt I32, countershaft 98, belt 9! and electric motor 16. When the carriage 32 reaches nearly the limit of its traverse to the left it will engage the stop 92 on the push rod 9|, see Fig. l, and slide the latter to the left as viewed in Fig. 10.

Movement of the push rod to the left causes the looped strap 98 thereon to actuate the lever I 89 to rock the over-center cam 82 to the position illustrated. in Fig. 5. During the rocking movement of the over-center cam 32 the spring pressed plunger 85 is pressed into the hollow arm 83 against the action of the spring 86 until the peak of the cam passes over the-center of the follower roller BI, after which the cam-face 88 acting on the follower roller rocks the actuating arm 80, rock-shaft II and casing 61 connected thereto to the position illustrated in Fig. 5. Thus, the worm-gear 55 is disengaged from the worm-wheel 63 and the worm-gear 54 is engaged immed ately therewith. Due to the rotation of the wormgear 54 and 55 in the same direction and their relative position at opposite sides of the wormwheel 53 the direction of rotation of the latter will be reversed. The direction of rotation of the sprocket 49 will also be reversed causing the carriage 32 to move to the right as viewed in Fig. 1.

The carriage 32 continues to move toward the right until it engages the stop 93 to actuate the push-rod!!! to the right as illustrated in Fig. 9. The over-center cam 82 is then rocked back to the position illustrated in Fig. 1, thereby causing the rock-shaft I! and casing 61 to be rocked to disengage the worm-gear 54 from the worm-gear 53 and engage the worm-gear 55 therewith. Thus, the reversing mechanism for the traversing means-is automatically operated to reverse the direction of traverse and the lawn-mower reel R is continuously rotated to produce cylindrical ground surfaces on the blades 1'.

If it is desired to operate the traversing means manually the sleeve GI on the shaft 56 is turned to aline the slot 63 therein with the pin 64 on the shaft. The spring 65 will then slide the sleeve BI to project its reduced end portion 62 into the circular hole I3 in the cover-plate I2 of the casing 57 when the latter is rocked into position, either manually or automatically, to aline the end portion of the sleeve with the hole. Engagement of the reduced end 62 of the sleeve (H with the periphery of the hole 13 in the casing 61 acts to hold the same in a neutral position as illustrated in Fig. 4, at which juncture both of the worm-gears 54 and 55 are disengaged from the worm-wheel 53. By turning the crank-handle 60 the shaft 56 may be turned in either direction and operating through the sprocket 49 and chain section 46, it will operate to traverse the carriage 32. To disengage the sleeve BI from the casing 61 it is only necessary to withdraw the sleeve toward the crank-handle 60 against the action of the spring 65 to disengagethe pin 54 from the slot 63. The sleeve 5i may then be turned to engage its end with theprojecting pin 64 to hold it withdrawn from the cover-plate I2 of the casing 67.

Although the traverse reversing mechanism has been described in connection with a lawn-mower reel R it will be understood that the reversing mechanism operates in the same manner to grind the stationary blades of a lawn-mower as illustrated and described in detail in the Carpenter patent, referred to above. To this end the stationary blade tobe ground is mounted on the arms I8 of the cradle and the latter rocked on its supporting shaft I3 to engage the notches 25 in the arms I8 with the bolts 26 and the wing nuts 21 are screwed onto the bolts and tightened against the arms to position the blade below the grinding wheel. The carriage 32 and grinding wheel 30 mounted thereon then traverse the stationary blade in the manner as explained above.

In the machine as manufactured it has been found desirable to provide gear-teeth on the worm-wheel 53 and worm-gears 54 and 55 in the nature of screw threads having a V-shaped contour with a relatively large included angle of approximately Thus, the sides of the teeth have a relatively fiat-slope pitch insuring easy engagement of the worm-gear 54 or 55 with the worm-wheel 53 and disengagement therefrom without clashing or burring of the gear-teeth. Preferably, the angular contour of the teeth of the gears 53, 54 and 55 and the eccentric pivot II for the casing 61 are so arranged that the tangential'component of movement of any part of the teeth of the worm-gear 5fi'or 55 as it moves away from the worm-wheel 53 will not cause binding engagement between the sides of the gear-teeth. In other words, if the slope or pitch of the sides of the teeth of the gears 53, 54 and 55 were too steep or the eccentric axis H of the casing 61. too close to the axis of the driven shaft 56 the rocking movement of the casingwould cause the sides of the teeth on the gear-wheel 54 or 55 to bear against the sides of the teeth on the worm-wheel as it moves away therefrom. It has also been found desirable to rotate the lawn-mower reel R in such manner as to cause the rear of its blades to first engage the grinding wheelas it rotates.

It. will be observed from the foregoing description that the present invention provides automatic reversing mechanism for driving the traversing means which is of relatively simple and compact construction and adapted to be mounted on standard machines as an attachment. It will also be observed that a drive is provided-for rotating the lawn-mower reel to be ground whereby to :produce cylindrical ground surfaces. It will still further be observed that the driving and reversing mechanism for the traversing means and the drive for rotating the lawn-mower reel may be driven by a common driving motor.

While a preferred embodiment of the invention is herein described and illustrated it is to be understood that modifications may be made in the structure and arrangement of the parts of the machine without departing from the spirit or scope of the invention. For example, other forms of gears or friction rollers may be used instead of the worm-gears illustrated in the drawings. Therefore, without limiting ourselves in this respect, we claim:

In a machine of the type indicated, means for mounting a lawn-mower reel having a shaft, a

drive shaft for rotating the lawn-mower reel, a dog having complementary .jaws adapted to he clamped at one end to one of the shafts, a clamping bolt extending throughlthe jaws, a threaded shank extending longitudinally of the jaws, a plug screwed onto the threaded shank and having pairs of stepped shoulders for engagement between the jaws at their ends, said plug being movable axially of the jaws by turning it on the threaded shank of the adjusting bolt to position one pair of shoulders between the jaws to adjust them to a diameter corresponding to the diameter of the shaft to which the dog is clamped, said dog having arms extending radially from the jaws, and a yokeshaped driving head detachably mounted on the opposite shaft having arms extending parallel to the axis of the shaft and interengaging with the radial arms on the dog for operatively connecting the two shafts.

JOEL P. MAYNARD. GEORGE A. MAT'I'ESON, JR. 

